This invention relates to a small watercraft such as a personal watercraft and, more particularly, to an improved exhaust system therefore.
Personal watercrafts are a popular type of watercraft in which one or more passengers ride on, rather than in, the watercraft.
Frequently, these watercrafts are sporting in nature, and the riders expect to leave the watercraft at times during its use and enter into the body of water in which the watercraft is operating.
Presently, one drawback of personal watercrafts is that unwanted noises are generated by the exhaust system upon the discharge of exhaust gases into the atmosphere. The conventional way of resolving this noise problem is to silence the exhaust noises by cooling the exhaust gases either through water jacketing the exhaust system or by dumping cooling water directly into the exhaust system and mixing the water with the exhaust gases. This water coolant is normally drawn from the body of water in which the watercraft is operating and then discharged back into the body of water along with the gases after being circulated through the exhaust system.
In a typical watercraft exhaust system, there is an exhaust manifold (often part of the engine itself) that discharges gas into an exhaust pipe. From the exhaust pipe, the gases move through an upwardly arched connector pipe or sleeve, an expansion chamber, another connector pipe, a resonator and then out of the watercraft. Generally, cooling water is introduced into the exhaust pipe to silence the noise generated from the exhaust gases. This water then moves along with the exhaust gases through the remainder of the exhaust system and is discharged.
The expansion chamber functions to trap the water to prevent it from flowing backwards into the engine. In many watercraft exhaust systems, the expansion chamber is normally positioned lower than the connector pipe connecting the exhaust pipe to the expansion chamber. In other words, this connector pipe is arched upward relative to the exhaust pipe and expansion chamber. Thus, once water reaches the expansion chamber, it is trapped and is difficult to flow backwards towards the engine.
One drawback with such a system is that since the connector sleeve following the exhaust pipe is arched upward, water often remains within the exhaust pipe and is often difficult to move forward. Typically, this water must be blown out of the exhaust pipe when the driver increases the throttle, the initial power blowing both the exhaust gases and the water upward through the connector sleeve and into the expansion chamber. When the watercraft is at low idle, water will not be blown out of the exhaust pipe and will accumulate since there is not enough power to blow it upward through the connector sleeve.
For several reasons, it is undesirable to have water remaining within the exhaust pipe. For one, the remaining water slows down the process of starting up the watercraft. This is because the remaining water must first be blown out of the exhaust pipe before the watercraft can be started. The occupants of the watercraft will often note a sputtering delay in starting the watercraft. That is, the water will sputter out of the watercraft for a few seconds before the engine becomes started. Water remaining in the exhaust pipes may also lead to undesirable corrosion and obstruction.
Thus, there is a need for an improved exhaust system for a personal watercraft capable of more effectively channeling water from an exhaust pipe into an expansion chamber while still allowing the expansion chamber to retain its water trapping functions. There is also a need for an improved watercraft system capable of starting rapidly, without the sputtering delay due to water being blown out.
In addition, there is a need for an improved exhaust system for a personal watercraft that occupies less hull space and can be packaged in a compact configuration. Furthermore, there is a need for an exhaust system that maintains the level of power needed for successful operation of the personal watercraft and allows for backflow protection to the engine.
According to a first aspect of the invention, there is provided a drainage system for a watercraft vehicle. The system includes an exhaust pipe, an expansion chamber; a connector sleeve and a water drain conduit. The connector sleeve is located between the exhaust pipe and the exhaust chamber and has a proximal end coupled to a first output of the exhaust pipe and a distal end coupled to a first input of the expansion chamber. The water drain conduit is located between the exhaust pipe and the exhaust chamber and has a proximal end coupled to a second output of the exhaust pipe and a distal end coupled to a second input of the expansion chamber. The second input of the expansion chamber is located below the first input of the expansion chamber and the second output of the exhaust pipe is locate below the first output of the exhaust pipe.
According to another aspect of the invention, there is provided a drainage system for a water vehicle. The system includes an exhaust pipe, an expansion chamber and a connector sleeve. The connector sleeve is located between the exhaust pipe and the exhaust chamber and has a proximal end coupled to a first output of the exhaust pipe and a distal end coupled to a first input of the expansion chamber. Means are located between the exhaust pipe and the exhaust chamber for draining water from the exhaust pipe.
According to a third aspect of the invention, there is provided a personal watercraft having a hull defining an engine compartment, a jet propulsion unit, a top deck and an exhaust system located in the engine compartment. The exhaust system includes an exhaust pipe, an expansion chamber, a connector sleeve and a water drain conduit. The connector sleeve is located between the exhaust pipe and expansion chamber and has a proximal end coupled to a first output of the exhaust pipe and a distal end coupled to a first input of the expansion chamber. The water drain conduit is located between the exhaust pipe and expansion chamber and has a proximal end coupled to a second output of the exhaust pipe and a distal end coupled to a second input of the expansion chamber. The second input of the expansion chamber is located below the first input of the expansion chamber and the second output of the exhaust pipe is located below the first output of the exhaust pipe.